Nuclear Magnetic Resonance (NMR) spectroscopy and imaging techniques have found application across a very broad range of subjects. Dynamic nuclear polarization (DNP) utilizes microwave irradiation of a coupled electron-nuclear spin system, in either a liquid or solid, to facilitate a transfer of polarization from the electron to the nuclear spin. As the magnetic moment of an electron spin is around three orders of magnitude larger than that of a nuclear spin (a factor of 660 for protons and 2640 for carbon-13), this results in a significant enhancement of the nuclear spin polarization. While DNP is becoming an increasingly important tool for signal enhancement in NMR, only certain materials seem to hyperpolarize efficiently using current techniques and it is important to understand why this is so, in order to broaden the scope of the technique.

The goal of the project is to develop methods to maximize the nuclear spin polarization that can be produced during DNP experiments. Improved understanding of the coupled electron-nuclear spin dynamics and the nuclear dipolar dynamics underlying DNP is central to developing improved control over the DNP process, which will then enable us to maximize the nuclear spin polarization achievable. The challenge to acquiring a detailed microscopic understanding of DNP dynamics lies in the fact that the process involves both open quantum system dynamics and many-body quantum dynamics, both of which can be challenging to understand. In this project we develop a detailed model for the open quantum system dynamics local to the site of the electron spins during DNP. These studies will enable us to identify the important pathways present for polarization transfer processes in DNP, and will allow us to develop optimal control strategies to maximize the polarization transfer efficiencies, both in terms of the maximum polarization achievable and the time taken to achieve it.

We have also built a novel an agile millimeter wave frequency system that allows us to generate arbitrarily shaped waveforms at millimeter wave frequencies for DNP. The accompanying DNP probe has been engineered to minimize both microwave and thermal losses during operation at liquid helium temperatures. The system incorporates a flexible source that can generate arbitrary waveforms at 94 GHz with a bandwidth greater than 1 GHz, as well as a probe that efficiently transmits the millimeter waves from room temperature outside the magnet to a cryogenic environment inside the magnet.